122 Regent St <1>
Feby 11/50
To H F Talbot Esqr
Sir
The slab I sent you was glazed I therefore assumed that it was not porous. A perfect glaze is non-absorbent.
I would ask you to break one of the slabs you can then prepare the transverse section that presents itself I find a thin vitreous coating at the sides. The centre is more absorbent than the part immediately under the vitreous part of the section.
It follows that slabs over-burned must have their surfaces removed so as to reach the centre where if the heat has not been too great a proper surface may be obtained In some experiments made with Cocker I first noticed that the centre of a mass of porcelain may be opaque & porous while the part near the surface ( of shown by a section) is translucent & impervious to moisture. –
This is fortunate because it may sometimes happen that the fire has been badly managed. Too much heat produced. The surface vitrified even when glaze has not been used.
In this case a little more grinding will bring us to the surface we require. –
I am trying to remove the glaze from Davenports<2> slabs by chemical agency I think grinding fills up the pores and will take some time to brush out.
I am, Sir, your obedient servant
T A Malone
Notes:
1. 122 Regent Street, London: base of Nicolaas Hennemans’ Talbotype or Sun Picture Rooms, later the firm of Henneman & Malone, photographers to the Queen.
2. Established in 1793 by John Davenport (1765-1848), at Longport, Burslem, Stafforshire.